1. Field of the Invention
This invention relates to valves, and more particularly, to temperature sensor valves in an engine or engine-driven accessory for altering the pressure of a fluid in response to at least a partial loss of coolant or an over-temperature condition.
2. Description of the Prior Art
In the operation of internal combustion engines, it is frequently desirable to provide protection means for automatically shutting off the engine or at least reducting its operating RPM to a safe level when certain conditions occur which would be detrimental to the engine or to an engine-driven accessory, such as an air compressor, hydraulic pump or transmission. To provide such protection, devices have been designed which are responsive to the temperature of the engine or accessory coolant. When the temperature of the coolant exceeds a predetermined value, these devices actuate an engine protection device such as a fuel shut-off valve which shuts off the fuel supply to the engine. A device of this type is disclosed in a patent issued to Goodwin (U.S. Pat. No. 3,302,143). However, devices such as these sense only the temperature of the engine coolant, whereas engine damage can occur when engine coolant is lost. Upon loss of engine coolant, the Goodwin apparatus will be ineffective since it will sense a low temperature because the coolant is no longer in contact with its temperature sensing probe. To protect an engine from damage due to loss of coolant, a separate coolant level sensor must be provided to operate in conjunction with the Goodwin device to prevent damage due to an engine over-temperature condition resulting from loss of engine coolant. The requirement for a separate coolant temperature sensor and a coolant level sensor substantially increases the cost of installation of these devices since each device must be separately installed on the engine and coupled to a separate engine protection means for shutting down the engine when a loss of coolant occurs or when an engine over-temperature condition exists.
A device which overcomes the above difficulty is disclosed in U.S. Pat. No. 4,126,114. In the latter patent, a temperature sensor is provided that senses the temperature of the engine block and which obtains heat from the engine block and transfers the heat to the engine coolant. Thus, an over heated temperature condition and/or the absence of an engine coolant will result in remedial action. In the type of valve described in the latter patent, oil from the engine lubricating system is admitted under pressure to a chamber that is sealed by a movable piston; upon detection of an over-heat condition, the piston is moved to open the chamber to an oil outlet port to thereby immediately reduce oil pressure and permit engine shut-down apparatus to begin the shut-off procedure. The piston operating in the bore is sealed against the bore through the use of O-rings; however, since there are passages communicating with the bore, damage to the O-ring sometimes occurs during assembly of the apparatus. The damage may not readily be apparent upon initial testing and will therefore fail after installation and during subsequent use.
Other types of engine protection devices for preventing damage due to an engine over-temperature conditions are disclosed in the following U.S. Pat. Nos. 3,153,403 (Dobbs), 2,125,066 (Cox), 1,869,429 (King), and 1,838,409 (King).